.clock {
    background-image: url(icons.jpg);
    background-size: 500% 400%;
    background-position: -100% -300%;
}
.school{
    background-image: url(icons.jpg);
    background-size: 500% 400%;
    background-position: 0 -200%;
}
.home{
    background-image: url(icons.jpg);
    background-size: 500% 400%;
    background-position: -200% -100%;

}